Sleep apnea is characterized by temporary cessation of breathing during sleep, which can lead to or aggravate many health problems. Obstructive sleep apnea (often abbreviated OSA) is primarily caused by the collapse of the upper airway. The base of the tongue has been found to be a common site of obstruction in the upper airway, and the upper airway dilator muscles have been recognized as being important in maintaining an open airway.
Unfortunately, current treatment methods for obstructive sleep apnea have not been consistently effective for all patients. The standard method is Continuous Positive Airway Pressure (CPAP) treatment, which requires the patient to wear a mask through which air is blown into the nostrils to keep the airway open. Patient compliance is poor due to discomfort and side effects, such as sneezing, nasal discharge, and dryness. A more recent treatment option, the implantation of rigid inserts in the soft palate to provide structural support, is both more invasive and generally is only effective for mild to moderate cases of obstructive sleep apnea. Alternative treatments are even more invasive and drastic, including tracheostomy and tissue ablation (somnoplasty or uvulopalatopharyngoplasty (UPPP)). Electrical stimulation of muscles has become another recent treatment option. These treatments have included direct electrical stimulation of muscle fibers, as disclosed in U.S. patent application Publication No. 2001/0010010 A1, and electrical stimulation of the hypoglossal nerve in a closed-loop system based on feedback from signals naturally occurring in the hypoglossal nerve, as disclosed in U.S. Pat. No. 6,456,866, for example.